The better you understand your engine's lubrication
system, the more you'll appreciate the vital role your oil filter
plays. When the engine is running, oil enters the oil pump through
a screened intake. The screened intake -- or oil pick-up -- is located
in the crankcase near the bottom surface of the oil pan. The oil
is drawn through the screen intake and forced by the oil pump through
the oil filter.
Oil from the main gallery is also fed through vertical
passages to the crankshaft main bearings and through the crankshaft
to the rod bearings. Oil thrown from the crankshaft, or sprayed
from the connecting rods, lubricates the pistons and cylinder walls.
In a typical full-flow type oil filter, the oil
flows into an inlet passage and then through the filtering element.
After flowing through the filter element, the filtered or "clean"
oil passes directly to the main oil gallery. In a partial-flow type
filter, the oil returns directly to the oil pan.
Oil from the main gallery lubricates the camshaft
and the camshaft bearings (and feeds hydraulic valve lifters if
used in the engine). On non-overhead cam engines, oil is metered
through the valve lifter to a hollow push rod that carries oil for
the lubrication of the push rod pivot point, rocker arm pivots and